I have a few questions about sr4 rules:
1. Can you switch between hot sim and cold sim if you have installed both on your commlink? If yes then how long does it take? Is it a free, simple or a complex action?
2. Can anyone provide a suggest a good cheat sheet to make hacking faster. Come to think of it a combat cheat sheet would be nice too.
3. Would a ranged adept be viable? As in an adept who focuses on ranged combat. If so what adept powers are best to pick up?

1. Unlikely possible by the hacker. SR4a, page 328, "As a precaution against hijacking, modified modules have a physical switch to change between cold and hot sim." Maybe a Free or Standard Action for someone else to flip that switch for the hacker, but under whatever circumstance it's possible the change wouldn't take effect until the start of your next Combat Turn (basis on Initiative and Actions for going from real space to Astral/Matrix).

3. Don't see why not. Improved Ability, Attribute Boost (Agility), Improved Physical Attribute, and Improved Reflexes are all obvious choices. The metamagic feat Attunement (Item) for your ranged weapon would also be good, though only builds as long as you keep initiating. That's only one line of thinking. There are many others I'm sure people will post here.

As far as ranged adepts, yes, I have a sniper adept personally, all of the abilities Spellbinder has, I took, also never overlook the usefulness of Adept Centering to ignore some penalties.

If there's not RAS Override active, it would be possible (as the hacker can still move his body). If there isn't, it is probably not possible (as the hacker cannot still move his body).

As for changes to initiative, the rule is that changes to the score apply immediately, reductions to the number of initiative passes apply immediately, but increases to the number of passes do not apply until the next combat turn.

Ok, but it should probably require a check right? what would the check be and what is the threshhold

Changing Modes from Hot VR to AR is a pretty easy action (I seem to remember Simple Action, but it might be a Free Action... been a while since I played a Hacker), at which point you can go to Cold Sim from there, and no switches need be flipped. Don't really see why you could not set up your link to switch between Cold Sim and Hot Sim in the same manner, though, assuming you want to take that risk. It is just changing Modes, after all.

Ranged Adepts are awesome. I have a Throwing Adept (Ninja) which is totally bad ass, though his range is limited to just at 100 Meters or so (give or take a few). A Gun Adept is pretty awesome too.

Unless you are being slammed (and locked online) by Black IC, then there is no test to change modes. Why should there be?

I just thought because you get -6 to all checks when you move your meat body while in VR it would be hard for you to focus enough to flip it.

In most cases, the existence of a stiff penalty is not cause to insert a test where none would be required normally.

Indeed...